Heart disease, specifically coronary artery disease, is a major cause of death, disability, and healthcare expense in the United States and other industrialized countries. In atherosclerosis, one form of heart disease, deposits of hard plaques (atheromas) may be formed within the intima of a vessel and inner media of arteries. This atherosclerotic disease process leads to a critical stenosis of the affected coronary artery and produces anginal syndromes, known commonly as chest pain. The progression of the stenosis reduces blood flow, triggering the formation of a blood clot (thrombus). The clot may further reduce or entirely prevent the flow of oxygen-rich blood to heart muscles, causing a heart attack. Alternatively, the clot may break off and lodge in the vessel of another organ, such as the brain, resulting in a thrombotic stroke.
One method for treating atherosclerosis and other forms of coronary narrowing is percutaneous transluminal coronary angioplasty (PTCA). During PTCA, commonly a balloon catheter device is inflated within the stenotic vessel. Upon inflation, the pressurized balloon exerts a compressive force on the lesion, thereby increasing the inner diameter of the affected vessel.
Soon after the procedure, however, a significant proportion of treated vessels restenose. To prevent restenosis, a stent may be implanted within the vessel. The stent acts as a scaffold to support the lumen in an open position and maintain lumen size. For insertion, the stent is affixed in a compressed configuration along the delivery catheter, for example crimped onto a balloon that is folded or otherwise wrapped about a guidewire. After the stent is properly positioned within the vessel, it is expanded, causing the length of the stent to contract and the diameter to expand.
Because stent insertion can cause undesirable reactions such as inflammation, infection, thrombosis, or proliferation of cell growth that occludes the passageway, stents are sometimes coated with therapeutic agents to assist in preventing these conditions. The coatings are bioengineered to release precise doses of the therapeutic agent. However, if the coating remains in direct contact with another material for an extended period of time, for example during shipping and storage, components of the therapeutic agent may migrate into the other material, resulting in delivery of a lower dose of the therapeutic agent than intended. Alternatively, components of a packaging material may migrate into the therapeutic coating, again leading to impaired performance of the therapeutic agent. Contact with packaging material may damage a coating even when it does not contain a therapeutic agent. Coated stents may also be damaged by exposure to ultraviolet radiation, and both coated stents and stents that have been surface treated may be affected by moisture in the air surrounding the stent.
Therefore, it would be desirable to have a packaged catheter system with improved protection for a treatment device such as a coated stent that overcomes the aforementioned and other disadvantages.